DE1745113B2 - PROCESS FOR THE PREPARATION OF COPOLYMERISATES CONTAINING HYDROXYL GROUPS - Google Patents

Description

25th

Polymers containing ester groups, such as, for example Vinyl acetate / olefin copolymers have hitherto been hydrolyzed in solution with the formation of Products which are useful in certain fields and which contain hydroxyl groups. It is so far however it has not always been easy to win the products, and other difficulties in controlling the response may arise.

In addition, it was already known that copolymers containing hydroxyl groups by hydrolysis of Copolymers of esters of unsaturated alcohols with saturated aliphatic monocarboxylic acids and others olefinically unsaturated monomers in the presence of lower alkyl alcohols in an amount that is less than the mixture of the copolymer starting material and alkaline conversion catalysts, in reaction vessels which are closed to the atmosphere and with thorough mixing (see German patent specification 7 63 840).

In the hydrolysis of such copolymers, however, it has been found time and again that these are in many cases does not proceed quantitatively or that the hydrolysis process can practically not be reproduced. This in turn has the consequence that products are obtained which, in terms of their properties, in particular solubility properties, differ - albeit slightly - from batch to batch.

For most uses, these are relatively minor property differences of subordinate importance; however, for some (special) purposes it is desirable and necessary to obtain a product that has strictly defined properties.

It is now obvious that in such a case one must endeavor to prevent the hydrolysis after one To carry out a process which allows absolutely uniform products, i.e. H. Products in always reproducible Quality without any difficulty to manufacture.

There has now been a process for the preparation of copolymers containing hydroxyl groups by hydrolysis of copolymers from esters of unsaturated alcohols with saturated aliphatic monocarboxylic acids and other olefinically unsaturated monomers in the presence of lower alkyl alcohols in an amount which is less than the weight of the copolymer starting material and alkaline reaction catalysts in which are closed to the atmosphere ^ and found with thorough mixing, in which this goal is achieved in that the other olefinically unsaturated monomer of the copolymer is an olefin, the ester content in the copolymer is 3-50% by weight and the reaction temperature is 30-150 ⁰ C is above the copolymer melting temperature.

In a preferred embodiment of the process according to the invention, the reaction is carried out at a pressure of 36.2 to 142 kg / cm ² . The unsaturated alcohol (which is normally aliphatic) from which the ester of the copolymer originates can be, for example, vinyl alcohol (conceptually), a substituted vinyl alcohol, allyl alcohol, methallyl alcohol or crotyl alcohol; it can also optionally be a cyclic alcohol, for example 2-cyclohexene-l- be ol. Suitable esters are, for example, those which have been formed by combining the alcohol with a saturated aliphatic monocarboxylic acid such as acetic, propionic, butyric, caprylic or stearic acid. The copolymers used with preference are copolymers of vinyl esters of a lower, saturated monocarboxylic acid, such as vinyl acetate or vinyl propionate, together with olefins.

However, a copolymer of two or more unsaturated esters can also be produced by the process of this Invention to be hydrolyzed. Suitable olefins are ethylene, propylene, 1-butene, isobutene or a higher homologue with either a straight or branched chain, for example 1-hexane or 2,2-trimethylpentene-1.

Two or more olefins can be present in the copolymer if desired. Ethylene is often a preferred comonomer. The ester fraction in a copolymer starting material is 3 to 50% by weight, for example 5 to 25% by weight.

In the hydrolysis reaction, the ester groups in the polymer starting material are replaced by hydroxyl groups replaced. Lower alkyl alcohol, such as methanol, ethanol, propanol or is used as the hydrolyzing agent Butanol used. An alkaline conversion catalyst such as the alkali metal derivative of alcohol is present. Quaternary ammonium hydroxides such as tetrabutylammonium hydroxide are also available useful. The preferred hydrolyzing agent is a solution of sodium methoxide or Lithium ethoxide in methanol.

It is not necessary that all of the ester groups in the polymer be hydrolyzed; for some purposes are partial hydrolysis e.g. B. up to 30% sufficient. In any case it is necessary that the Hydrolyzing agent in a sufficiently stoichiometric ratio to hydrolysis of the polymer in the desired degree is present. The weight of the hydrolyzing agent is less than the weight of the Copolymer starting material. The catalyst is used in an amount up to 5% by weight of the hydrolyzing agent, for example used from 0.1 to 2 wt .-%.

The copolymer is in the molten state, and the reaction temperature is therefore naturally higher than that at which the copolymer melts, namely 30 to 150 ^° C. higher than

the one in which the copolymer melts. The hydrolyzing agent can make the polymer soft and therefore cause the melting point of the polymer is lowered, in some cases up to 3O ⁰ C under the normal value, and this effect makes it necessary to provide them in the selection of an appropriate reaction temperature into account.

To carry out the hydrolysis above the Copolymerisatschmelztemperatur, namely after all, still 30 to 150 ⁰ C above, there was no plausible reason the melting temperature of the copolymer: there was rather a prejudice against it, carry out the hydrolysis at such high temperatures; This is because it had to be expected that at the high temperatures used, the copolymer would suffer degradation and, as a consequence, even more products would be obtained which differ from batch to batch in terms of their quality or properties.

So there was an expertly established probability that at high temperatures uneven products are obtained due to the expected degradation reactions.

The process can in appropriate cases be carried out at atmospheric pressure, but very often the use of an elevated pressure is necessary in order to avoid evaporation of the hydrolyzing agent. The hydrolyzing agent can be present as a gas or vapor. The pressure is preferably in the range from 0.35 to 352 kg / cm ^2, for example from 36.2 to 142 kg / cm ² .

The process can be carried out batchwise or as a continuous process. It will be in one Reaction kettle which is sealed against the atmosphere and heated to a suitable temperature can be carried out. Agitation means are preferably required and, for example, it is appropriate to use an internal mixer as a reaction vessel. A time from a few seconds to several minutes is normally necessary for the reaction to proceed, and for example a period of time is between 10 seconds and 30 minutes, often between 25 seconds and 10 minutes, usually sufficient. The hydrolysis can continue until essential equilibrium is reached, or it can go to one Intermediate stage are stopped. When the hydrolysis is complete, the pressure in the reaction vessel is released and the hydrolyzed polymer removed. An excess of hydrolyzing agent and the catalyst residues can be removed by washing with a suitable liquid, for example water however, washing is usually not essential.

For a continuous hydrolysis process, the use of a kneader or a screw extruder is particularly suitable, where the hydrolyzing ^either: n the Maschinenfüütricher together with the Polymerisatausgangsmaterial or preferably, especially separately injected into the interior of the machine to a point where already some heat softening of the polymer occurred Has. The hydrolysis reaction then proceeds as the mixture is moved forward through the machine and with a suitable adjustment of the conveying ratio the residence time can be selected so that the reaction has proceeded to the desired extent in the time the mixture takes Exit of the machine reached.

It is also possible to use a continuous hydrolysis process in the extruder of a blow molding machine or in the preplasticizing section of a screw preplasticizing injection molding machine, so that molded objects can be produced immediately.

In general, have the hydrolyzed, according to the invention manufactured products greater toughness, ίο or breaking strength than the polymers of which they originate, and it has been found in some cases that when they are in an oriented form, such as prepared by stretching a thread or film of the hydrolyzed polymer will have significantly improved tensile strength.

The invention is illustrated by the following examples.

example 1

This example describes the continuous production of a copolymer with hydroxyl groups by hydrolysis of a molten copolymer of ethylene and vinyl acetate, this being 12.5% Contained vinyl acetate.

The copolymer used was a copolymer of 87.5% by weight of ethylene and 12.5% by weight of vinyl acetate. The copolymer was passed through an extruder at a rate of 15 g / min, which had a cylinder 2.54 cm in diameter and 61.0 cm in length. The mean temperature of the copolymer in the cylinder was 15O ⁰ C. 27.9 cm from the inlet opening of the extruder cylinder was injected at a rate of 6 g / min, a solution of l, 4 wt .-% sodium methoxide in methanol. The residence time of the copolymer after the methanol was injected was about 1 minute and at the end of the extruder it was extruded into the atmosphere through a simple, round nozzle outlet with a diameter of 0.762 mm. The extruded polymer was cooled and broken into small tablets.

This product could be processed by injection molding extrusion molding, blow extrusion molding or blow molding. It was harder than the original starting copolymer and it resulted from the change in the optical density of a thin film of the polymer at a wavelength of 5.7 microns (CO absorption) compared to that at a wavelength of 6.7 microns (CH _{2 absorption} ) calculated that 83% of the acetate groups had been hydrolyzed to hydroxyl groups.

Example 2

This example describes a number of continuous hydrolysis reactions in which the copolymer of Example 1 was used under a variety of reaction conditions.

do A number of the hydrolysis reactions were carried out in the in Example 1 was carried out in the manner described, but using different modes and ratios of catalysts and various extrusion cylinder temperatures, as shown in the following Table can be seen. The table also shows the degree of hydrolysis (determined as in Example 1), which in was achieved in each case. (The hydrolyzing agent was methanol in all cases.)

catalyst catalyst Strand preli- degree of temperature Hydrolyte ization. Wt% % Sodium methoxide 0.3 150 25th Sodium methoxide 0.7 150 23 Sodium methoxide 3.0 225 78 Lithium methoxide 0.5 150 32 Tetrabutyl 4.0 150 7th

ammonium hydroxide

It was found that all of the products were harder and stronger than the starting copolymer, the change becoming more noticeable as hydrolysis increased.

Example 3

This example describes the preparation of two further copolymers containing hydroxyl groups by the continuous hydrolysis of 2 copolymers of ethylene and vinyl acetate, whereby each contained a higher proportion of vinyl acetate than the copolymer used in Example 1.

The two copolymers used contained 30 and 45% by weight of vinyl acetate, respectively, with the balance Ethylene was. Each was hydrolyzed according to the procedure described in Example 1 and was im the first case found that the degree of hydrolysis was 80%, while in the second case it was 34%.

It was again found that the products obtained were harder and stronger than the starting copolymers.

Claims (2)

Patent claims: 1. Process for the preparation of hydroxyl-containing cooolymerizates by hydrolysis of copolymers from esters of unsaturated alcohols with saturated aliphatic monocarboxylic acids and other olefinically unsaturated monomers in the presence of lower alkyl alcohols in an amount less than the weight of the copolymer starting material, and alkaline Conversion catalysts in reaction vessels that are closed to the atmosphere are, and characterized by mixing that the other olefinic (5th unsaturated monomers of the copolymer is an olefin, the ester portion in the copolymer 3-50% by weight and the reaction temperature is 30-150 ° C. above the copolymer melting temperature lies. 2. The method according to claim 1, characterized in that it is carried out at a pressure of 36.2-142 kg / cm ² .